Stitch control mechanisms and thread cutter

ABSTRACT

Stitch control mechanisms modify a sewing machine to provide for the sewing of variably spaced stitches and provide for the control of the last stitch in a terminating series and the initial stitch in a subsequent series by severing only the bobbin supplied portion of these stitches and positioning the free ends thereof adjacent to a workpiece.

United States Patent Olney, Jr. 1 Oct. 31, 1972 [54] STITCH CONTROL MECHANISMS AND 1,369,371 2/1921 Allen ..112/252 THREAD CUTTER 3,139,849 7/1964 Cohen et a1. ..112/252 3,173,393 3/1965 Adam ..112/252 [723 gi' 'f 3,386,402 6/1968 R088 ..112/252 3,554,149 1/1911 Diehm ..112/252 [73] Assignee: Honeywell Information Systems, 3,425,376 2/1969 Brynge et al ..1 [2/220 hm, w th M 3,433,189 3/1969 Weisz ..112/221 X [22] Filed: 1971 Primary Examiner-James R. Boler 2 APPL 103,503 Attorney-Fred Jacob and Edward W. Hughes 5 7] ABSTRACT [52] 11.8. C1 ..112/252, 112/221 [51 161. c1. ..D05b 65/02 Stitch Control mechamsms modlfy 8 machme [5 Field of Search z/zsz 220 221 12 1 10 provide for I118 sewing Of variably spaced stitches llzllzLn i and provide for the contro1 of the last stitch in a terminating series and the initiai stitch in a subsequent series by severing only the bobbin supplied portion of [56] References Cited these stitches and positioning the free ends thereof ad- UNITED STATES PATENTS J'acem a wofkpiece- 2,768,593 10/1956 Lombard ..112/221 X 11 Claims, 15 Drawing Figures -VillllllllI PHENTEDHBIEH I972 SHEET 3 BF 4 [El INVENTOR.

1 STITCH CONTROL MECHANISMS AND THREAD CUTTER BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to control mechanisms and more particularly to stitch control mechanisms for a sewing machine.

2. Description of the Prior Art The stitch control mechanisms of the present invention are used on a sewing machine to provide for the sewing of unevenly spaced stitches and to provide controlled positioning of the free ends of severed stitches. A particular application for stitch controls of this nature is when conductive wire is sewn into circuit boards.

A method for conducting electrical signals to selected areas of a circuit board by the sewing of conductive wire therein is fully disclosed in copending US. Pat. application, Ser. No. 39,728, filed May 22, 1970, by the same inventor as the present application and assigned to the same assignee.

That method, briefly described, comprises the sewing of insulated conductive wire into apertures formed in solder coated conductive areas or pads of the circuit board. The conductor is sequentially sewn into a predetermined series of pads to form a discrete signal path. The conductor is then cut and another signal path may then be sewn. The sewing and cutting continues until all the desired signal paths are installed. Heat is then applied to the pads to melt the insulation on the loops of the conductors which are sewn into the apertured pads. This same heat also reflows the solder thus tacking the conductors in place.

The solder coating is applied to the pads by a plating process which results in a relatively thin deposition. Therefore the apertures re main substantially open after the above described heating step so that the leads of electrical elements such as integrated circuit packages, transistors, and the like may be inserted therein. The circuit board is then flow soldered in the normal manner to form electrical connections between the leads, conductors, and the conductive areas.

The sewing of conductors into circuit boards is accomplished by a modified sewing machine on which the insulated wire is wound on the bobbin, and a nonconductive material such as thread is supplied to the needle from a spool. The thread is employed in the initial forming of the stitch, and is used to provide a temporary holding means for the conductive wire until it is soldered in place as described.

Since sewing techniques are employed to implement the sewing of conductive wires into circuit boards, a study was made of the sewing machine art and it was soon realized that conventional sewing machines lack the necessary control mechanisms for this special purpose.

A conventional sewing machine is adapted to sew a series of evenly spaced stitches, whereas the sewing of conductive wire into circuit boards to form discrete circuits requires the sewing of unevenly and variably spaced stitches. The spacing between stitches may vary from a fraction of an inch to several inches within a single discrete circuit path. I

Several types of stitch cutting devices are available usually on industrial or commercial sewing machines.

These prior art devices operate in various ways and generally sever both the needle and the bobbin supplied portions of the stitch. The sewing of conductive wire into circuit boards employs the needle supplied thread as a temporary holding means for the bobbin supplied wire. Therefore, it is desirable that one continuous thread be used to hold all the discrete circuits in a circuit board to insure firm holding thereof and to eliminate the need for anchoring the thread each time a discrete circuit path is started and ended.

in conventional sewing such as on garments and the like, the free ends of severed stitches do not present problems so they may be left dangling. It is well known in the circuit board art that the free ends of wires cannot protrude or be left dangling from a circuit board.

Therefore, in a view of the foregoing, the need exists for stitch control mechanisms which provide for the sewing of variably spaced stitches which cut only the bobbin supplied portion of a stitch and which position the free ends of the cut stitch adjacent to a workpiece.

SUMMARY OF THE INVENTION In accordance with the invention claimed, new and useful stitch control mechanisms are disclosed which modify a conventional sewing machine to provide for the sewing of variably spaced stitches which cut only the bobbin supplied portion of a stitch and which position the dangling end of the cut stitch adjacent to a workpiece.

The stitch control mechanisms of the present invention include a positioning means connected to the sewing machine for precision control of the stitch forming mechanisms thereof. The positioning means allows a maximum of one stitch to be sewn, and then holds the machine inoperative until a command is received to form another stitch. This type of stitch control provides the machine with the capability of being used to form variably and unevenly spaced stitches by allowing time between the formation of the stitches for a workpiece to be moved to the next area into which a stitch is to be sewn.

The positioning means may also be employed to stop the movement of the stitch forming devices at any point during the formation of a stitch so that a stitch cutting means of the present invention may cut the bobbin supplied portion of the stitch prior to completion thereof. By cutting the bobbin supplied portion of a stitch prior to its completion, the free end of the cut stitch will be moved adjacent to the workpiece when the stitch is completed.

A first cutter device is employed to cut the bobbin supplied portion of the last stitch in a terminating series, and a second cutter device is used to cut the bobbin supplied portion of the first stitch in a subsequent series. When these two operations are performed in sequence a small loose piece of the bobbin supplied material results, which may be removed by conventional methods such as a vacuum device.

Accordingly, it is an object of the present invention to provide new and useful stitch control mechanisms.

Another object of the invention is to provide a new and useful sewing machine control device which permits the sewing of unevenly spaced stitches.

Another object of this invention is to provide a new and useful stitch control mechanism which cuts the stitch prior to completion thereof so that the free end will move adjacent to a workpiece upon completion of the stitch.

Another object of this invention is to provide a new and useful stitch control mechanism which causes a sewing machine to form one stitch and then holds the machine inoperative until a command to form another stitch is received.

Another object of the invention is to provide a new and useful sewing machine control device which allows needle movement to be stopped at any point during the forming of a stitch.

Another object of this invention is to provide a sewing machine control device which cuts only the bobbin supplied portion of the stitch and positions the free end adjacent to a workpiece.

Still another object of the present invention is to provide new and useful stitch control mechanisms for cutting the last stitch in a terminating series of stitches and the initial stitch in a subsequent series and positioning the free ends adjacent to a workpiece.

And yet another object of this invention is to provide new and useful stitch control mechanisms which adapt a sewing machine to perform the special functions associated with sewing conductive wire into circuit boards.

The foregoing and other objects of this invention, the various features thereof, as well as the invention itself, may be more fully understood when read in conjunction with the accompanying drawing.

BRIEF DESCRIPTION OF THE DRAWING FIG. I is a perspective view of the sewing machine and associated mechanisms incorporating the features of the present invention;

FIG. 2 is a fragmentary front elevation view of the mechanism of the present invention;

FIG. 3 is a fragmentary side elevation view, partially in section, illustrating some of the features of the present invention;

FIG. 4 is a sectional view taken on the line 4-4 of FIG. 3;

FIG. 5 is a sectional view taken on the line 5-5 of FIG. 4;

FIG. 6 is a sectional view taken on the line 6-6 of FIG. 5; and

FIGS. 7-15 are enlarged sectional views partially in schematic form illustrating the various positions and functions of the stitch cutting and positioning devices of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring more particularly to the drawing, FIG. 1 illustrates a system 10 which includes mechanisms and apparatus for sewing electrical conductors into circuit boards. The system employs a conventional X-Y plane positioning table 12, a sewing machine 14, a controller 16, and a special pedestal 18 on which a circuit board 20 is mounted.

It should be noted that the system 10 represents an ideal fully automated system and that the present invention may be practiced with less elaborate equipment.

The X-Y table is provided with its usual base 22 having a movable bed 24 mounted thereon in the well known manner. The pedestal 18 is mounted on the movable bed 24 and has a cantilever plate 26 suitably attached to its upper end 28. The plate 26 which extends from the pedestal 18 is disposed parallel with respect to the movable bed 24 and is provided with mounting clips 30 on an extending edge 32 thereof, to which the circuit board 20 is affixed. Therefore, with the circuit board attached to the movable bed 24 as described, the well known precision positioning capabilities of the X-Y table 12 results in accurate positioning of the circuit board.

The sewing machine 14 may be any commercially available model which has been modified to accomplish the special purpose functions needed in the sewing of conductive wire into circuit boards.

As best seen in FIGS. 1, 2, and 3, the sewing machine 14 is provided with an enlarged work support bed 34 which is mounted on a pair of cantilever beams 36 extending from the back 38 of the X-Y table 12. The support bed 34 extends outwardly from a rear frame 38 of the X-Y table 12 and is disposed parallel with respect to the movable bed 24 of the table. The bed 34 is also parallel with respect to the circuit board and is positioned below it to provide a bearing surface upon which the circuit board will move.

The sewing machine 14 is equipped with the normal enclosing frame, best seen in FIG. 3, which includes a vertical standard 40 having a base portion 42 at its lower end for mounting on the support bed 34. Exte nding outwardly from the upper end of the vertical standard 40 is an overhanging arm 44 which at its outer end has a head 46 in which is mounted a vertically reciprocatory needle 48. It will be understood that suitable connections (not shown) are provided from a main drive shaft 50, mounted in the frame of the machine, to operate the needle 48 and cooperating stitch forming means such as a bobbin 57 (FIG. 4).

Power is supplied to the machine 14 by a special motor 54 coupled directly to the main drive shaft 50. The motor 54 provides a portion of the special stitch control mechanisms of the present invention as will hereinafter be described in detail.

The controller 16 is a conventional analogue device which is coupled to both the sewing machine 14 and to the X-Y table 12 to coordinate the stitch forming mechanisms with the circuit board positioning in accordance with a special program.

The sewing of conductive wire into selected apertures of a circuit board is accomplished by the sewing machine 14 having conductive wire on the bobbin thereof and having a nonconductive material such as thread supplied to the needle from a spool. Stitches are formed in the conventional manner by the stitch forming mechanisms whereby the needle carries the thread down through the aperture in the circuit board. The thread is looped around the bobbin supplied wire and formed into a loop which is pulled into the aperture by the return stroke of the needle and the thread take-up lever. For reasons to be hereinafter described, stitching performed on a medium having the special requirements of a circuit board necessitates special stitch control mechanisms which provide for the sewing of unevenly spaced stitches, and cuts only the bobbin supplied portions of initial and terminal stitches in a series and positions the free ends thereof adjacent or within the circuit board.

The sewing of unevenly spaced stitches is needed so that areas to be electrically connected in forming a discrete circuit path may be located any place within the confines of the circuit board. That is, the next area requiring a stitch (electrical connection) may be adjacent to or several inches from the last stitch.

The stitch spacing function is accomplished by the motor 54 which, as previously described, supplies power to the sewing machine. In the preferred embodiment the motor is a pulse operated stepping motor which allows precise control of the stitch forming mechanisms.

Pulse operate stepping motors are well known in the art, therefore the functions thereof will be only briefly described. Motors of this type generally operate on pulsating DC. and, depending on the particular motor, require a specified number of pulses to complete a single revolution. For example, a motor requiring 360 pulses to complete a single revolution will step 360 times in completing that revolution. It is apparent that coupling the motor of the above example to the sewing machine 14 would allow the stitch forming mechanisms to be stopped at any one of 360 positions in one motor revolution. The stitch spacing function may therefore be accomplished by applying one series of pulses to the motor 54 until one stitch is completed. The motor is then held inoperative until the next series of pulses are applied to form the next stitch. This type of operation allows as much time as is necessary for the X-\ table to move the circuit board so that the next area to be stitched is accurately positioned with respect to the stitch forming mechanisms of the machine 14.

As hereinbefore stated, the nonconductive thread is supplied by a spool 51 in the formation of stitches via a tensioning device 52 and the needle 48 in the normal manner. The thread is used as a temporary holding means for the conductive wire until it is soldered in place. To terminate a circuit path, only the conductive wire needs to be severed, as the thread plays no part in the electrical characteristics of the circuit. Therefore, one long continuous thread may be used for holding all of the wires in the discrete circuits within a circuit board, thus insuring that the wires will be firmly held in place until the soldering operation is performed.

As in a conventional sewing machine, a stitch forming device 55 is located in the work support bed 34. As best seen in FIGS. 2, 3 and 4, the stitch forming device 55 is located directly below the head 46 of the machine. Since it is desirable to perform the cutting operations only on the bobbin supplied portion of the stitch, the stitch forming device 55, which includes a bobbin 57 and its associated devices, has been modified to include a stitch cutting means 56, see FIGS. 4, 5 and 6.

Referring now to FIGS. 4, 5 and 6, the support bed 34 is provided with the usual aperture 58 formed therethrough which is located below and in coaxial alignment with the needle 48 so that the reciprocating movement of the needle may cooperate with the bobbin 57 to form stitches in the normal manner.

A first cutter mechanism 60, adapted to cut the bobbin supplied portion of a terminating stitch is pivotably attached to a lower surface 62 of the support bed 34 and comprises a lever 64 having a pivot screw 66 carried in a suitable bushing 68 located intermediate the ends of the lever 64. One end of the lever 64 is provided with an aperture 70 therethrough which in the relaxed or noncutting position of the cutter means 60 is coaxially aligned with the aperture 58 of the bed 34 and is therefor in alignment with the needle. The other end of the lever 64 is provided with a downwardly depending pin 72 having a suitable control rod 74 connected thereto. The rod 74 is coupled on its other end to a servo (not shown) which upon receiving a signal from the controller 16 will actuate the first cutter means 60 from the solid line position (FIG. 5) to the dashed line position. As seen in FIG. 4, the upper surface of lever 64 is in contiguous engagement with the lower surface 62 of the bed 34 so that a knife edge 76 provided on aperture 70 cooperates with a similar knife edge 78 provided on aperture 58 to perfonn the cutting operation.

A holding means 80 which is adapted to hold the bobbin supplied portion of the stitch during the cutting operations is mounted below first cutter means 60 on a horizontally reciprocating bar 82. The bar 82 is reciprocated by a servo (not shown) connected thereto which, upon commands received from the controller 16, will move from the solid line position (FIG. 5) to the dashed line position. The holding means 80 comprises a holding plate 84 which is attached to the bar 82 by suitable screws 85 and is provided with a gripping surface 86 which moves adjacent to a gripper block 87 when the holding means is moved to the dashed line position. When the holding means 80 is moved into the holding or gripping position, it will deflect the bobbin supplied material, in the embodiment being described a conductive wire, from its normal path and hold it so that the initial stitch may be subsequently formed.

A second cutter means 88, which is adapted to cut the bobbin supplied portion of an initial stitch, is reciprocally mounted in a downwardly facing slot 90 formed in the lower surface of the holding plate 84 of holding means 80. The second cutter means 88, as best seen in FIG. 6, includes an elongated vertically disposed plate 92 having a control rod 94 connected to one end thereof so that movement supplied to the rod 94 by a suitable servo (not shown) will move the plate 92 from the solid line position to the dashed line position. A notch 96 is formed in the lower part of the plate 92 and is positioned to slidingly engage the reciprocating bar 82 to limit the movements of the plate 92. The other end of the plate 92 is provided with a downwardly disposed cutter notch 98 which performs its cutting operation'when moved relative to a cutting channel 100, see FIG. 4, formed in the lower part of the plate 84 and transversely disposed with respect to the slot 90 formed therein.

A removal means 101 (FIG. 5) such as a vacuum duct 102 is located in the vicinity of the above described cutting and holding devices to carry away loose fragments of the severed stitches as will hereinafter be described in detail.

The purpose, operational sequence, and timing of the cutting and holding devices may be more fully understood by considering FIGS. 7-15 and the following description associated therewith.

FIGS. 7-15 are enlarged fragmentary schematic illustrations, each showing the circuit board 20 with the apertures 102 formed therethrough. For illustrative purposes, the apertures 102 are shown as being adjacent to each other and it should be understood that they may be located any place on the circuit board as previously described. All of the stitch forming and tensioning referred to in the following operational description of the devices of the present invention can be accomplished by conventional sewing machine devices that are old in the art, and are therefore not shown or described in detail.

FIG. 7 shows a nonconductive thread 104 holding a conductive wire 106 within one of the apertures 102, thus forming a normal stitch 108. Stitch 108 is to be considered as the second to last stitch in a discrete circuit path so that the next stitch to be formed will be a terminal stitch 110.

In FIG. 8, the circuit board has been moved such that aperture 102 which is to receive the terminal stitch 110 is in the proper position. The needle (not shown in FIGS. 7-15) has cooperated with the bobbin (also not shown in FIGS. 7-15) to form the terminal stitch 110. The needle is then immediately started through another cycle to form a double stitch, or restraining loop 112. The restraining loop 112 is formed on the upper portion of the terminal stitch 110 to insure that the next movement of the circuit board will not pull the terminal stitch out of its aperture. In forming the restraining loop 112, the needle movement is stopped or pauses just short of completing its cycle so that the thread 104 which was payed out during the downward stroke of the needle has not been completely taken up, that is, it still contains some slack.

In FIG. 9, the holding means 80 has been actuated which deflects the conductive wire 106 out of its normal path. The movement of the wire 106 needed to complete the deflection will come from the stitch side of (above) the holding means 80 due to the slack in the thread. This movement will pull the stitch 110 down within the aperture as shown.

In FIG. 10, the first cutter means 60 is then actuated to complete its cutting of the conductive wire. Needle motion is resumed to cause it to complete its cycle, which by the conventional thread take-up lever (not shown) moves the terminal stitch 110 and the restraining loop 1 12 up within the aperture. This action completes the formation and securing of the terminal stitch, and as shown positioned a free end 114 thereof within the aperture.

In FIG. 11, the circuit board 20 has been moved to another location where it is to receive an initial stitch 116 of a new circuit path. The needle is actuated through a complete cycle to form the initial stitch 116. Rather than allowing the initial stitch to be pulled up into the aperture, the upward motion of the wire 106 is stopped at the location shown by increasing the bobbin tension thus causing the thread 104 to pay from the spool rather than paying the wire 106 from the bobbin. Also seen in this illustration, a portion 118 of the wire 106 located between the initial stitch and the free end being held by the holding means 80, will move up into the cutter channel 100 of the holding means.

In FIG. 12 the needle is then started through another cycle to form a restraining loop 120. The motion of the needle is stopped on the return stroke of its cycle to position the restraining loop 120 in the same location as the stitch.

FIG. 13 shows the second cutter means 88 having cut the portion 118 of wire 106.

In FIG. 14, the needle motion is resumed to complete its cycle which, by allowing the bobbin tension to remain high, will cause the thread which was previously payed-out to slide along the wire until the restraining loop cycle is complete. As shown, when this cycle is completed, the initial stitch 116 and the restraining loop 120 will have moved up to a normal position within the aperture and a free end 124 of the initial stitch will be positioned within the aperture 70. The holding means has moved back to its relaxed position thus releasing a loose fragment 126 of wire which may be disposed of by the removal means 101, such as the vacuum duct 102 (FIG. 5).

In FIG. 15, the circuit board 20 has now been moved to a new location where a second stitch 128 in the new circuit path has been formed. In FIGS. 7-15, the free ends of the terminal and initial stitches were shown as positioned within the apertures. It should be noted that this precise positioning is dependent on several factors which are: circuit board thickness, support bed 34 thickness, and the vertical dimensional relationships of the cutting and holding devices. As in all mechanisms, these factors will vary within specified tolerances which may result with the free ends being positioned further within the apertures than shown, or protruding slightly therefrom. These slight positional variations will not cause a problem as long as the free ends are close or adjacent to the bottom surface of the circuit board.

It should be apparent the control of the needle positions within a single cycle may be accomplished by supplying only enough pulses to the motor 54 to cause it to step to the desired spot and motion may be resumed by applying the remaining pulses thereto. This function could also be accomplished by any command responsive positioning means such as indexing mechanisms, solenoid controlled mechanical stops, incremental indexing servo mechanisms, and the like.

The second cutter means 88 and the holding means 80 need only be employed when a new circuit path is to be started after completion of a previous circuit path. That is, termination of a stitch may be accomplished by causing the needle to pause at which time the wire is severed so that upon completion of the stitch normal stitch forming functions will cause the free end to pull up adjacent to the aperture.

Although the bobbin supplied material is shown as a conductive wire for purposes of interconnecting conductive wires on a printed circuit board, it is obvious that any filament may be used for either the bobbin supplied material or for the spool supplied material (the thread in this preferred embodiment). Also in the preferred embodiment a printed circuit board is used as the workpiece that is stitched by the apparatus of the present invention. It is obvious that other material could be used such as cloth onto which a pattern comprising unevenly spaced stitches is to be sewn by the use of the present invention.

Thus, while the principles of the invention have now been made made clear in an illustrative embodiment, there will be immediately obvious to those skilled in the art many modifications of structure, arrangement, proportions, the elements, materials, and components, used in the practice of the invention, and otherwise, which are particularly adapted for specific environments and operating requirements without departing from those principles. The appended claims are therefore intended to cover and embrace any such modifications, with the limits only of the true spirit and scope of the invention.

What I claim is:

l. A stitching mechanism for a sewing machine for severing of a bobbin supplied material of a stitch and for positioning a free end of the bobbin supplied material adjacent to a workpiece, said mechanism compnsmg:

a stitch forming mechanism forming stitches in a workpiece, said stitch forming mechanism including a bobbin supplying a strand material for the stitch forming mechanism;

selectively actuatable positioning means coupled to said stitch forming mechanism for causing a pause in a movement of the stitch forming mechanism prior to completion of the stitch; and

cutter means movably mounted for severing the bobbin supplied material during the pause prior to completion of the stitch caused by said positioning means to form a free end on the bobbin supplied material, the free end being moved adjacent to the workpiece by the stitch forming mechanism when it completes the stitch.

2. A stitching mechanism as claimed in claim 1 wherein said positioning means comprises a pulse operated stepping motor.

3. A stitching mechanism as claimed in claim 1 wherein said cutter means comprises:

a lever movably mounted on the lower surface of the workpiece support bed and in contiguous engagement therewith;

means coupled to one end of said lever for providing movement thereto; and

a knife edge formed on the other end of said lever to cooperate with the workpiece support bed for severing the bobbin supplied material when said lever is moved relative to the bed.

4. A stitching mechanism for a sewing machine for controlling the severing of a bobbin supplied material to form a first free end on a terminal stitch in a terminating series and to form a second free end on an initial stitch in a subsequent series and for positioning both the first and the second free ends adjacent to a workpiece, said mechanism comprising:

a stitch forming mechanism forming stitches in a workpiece, said stitch forming mechanism including a bobbin supplying a strand material for the stitch forming mechanism;

selectively actuatable positioning means coupled to said stitch forming mechanism for causing a pause in the movement of the stitch forming mechanism prior to completion of the terminal stitch and for causing another pause in the movement of the stitch forming mechanism prior to completion of the initial stitch;

first cutter means mounted adjacent to the bobbin for severing the bobbin supplied material during the pause prior to completion of the terminal stitch to form the first free end thereon, the first free end being pulled adjacent to the workpiece by the stitch forming mechanism when it completes the terminal stitch;

holding means mounted below said first cutter means for holding the severed bobbin supplied material, and for deflecting the bobbin supplied material into position for the formation of the initial stitch thereon; and

second cutter means mounted below said holding means for severing the bobbin supplied material during the pause prior to completion of the initial stitch to form the second free end thereon, the second free end being pulled adjacent to the workpiece by the stitch forming mechanism when it completes the initial stitch.

5. A stitching mechanism for a sewing machine for controlling the formation of a terminal stitch in a terminating series and an initial stitch in a subsequent series, said mechanism comprising:

a stitch forming mechanism forming stitches in a workpiece, said stitch forming mechanism including a bobbin supplying a strand material for the stitch forming mechanism;

selectively actuatable positioning means coupled to said stitch forming mechanism for causing a pause in the movement of the stitch forming mechanism prior to the completion of the terminal stitch and for causing another pause prior to completion of the initial stitch;

first cutter means movably mounted below a workpiece support bed of the sewing machine for making a first cut in the bobbin supplied material to form a first free end on the terminal stitch during the pause prior to completion thereof, the first free end being moved adjacent to the workpiece by the stitch forming mechanism when it completes the terminal stitch; gripper block fixedly mounted below the workpiece support bed of the sewing machine;

a holding plate movably mounted below said first cutter means and in alignment with said gripper block for deflecting the bobbin supplied material into holding engagement with said gripper block so that the initial stitch may be formed on the bobbin supplied material after severing and completion of the terminal stitch, said holding plate having a cutting channel formed in the lower surface thereof into which the bobbin supplied material moves during formation of the initial stitch, said holding plate further having a slot formed in the lower surface thereof; and

second cutter means movably mounted in the slot formed in said holding plate for cooperating with the cutting channel thereof to make a second cut in the bobbin supplied material during the pause prior to completion of the initial stitch to form a second free end thereon, the second free end being moved adjacent to the workpiece by the stitch forming mechanism when it completes the initial stitch.

6. A stitching mechanism as claimed in claim 5 wherein said second cutter means comprises a plate having a cutter notch formed in one end thereof for cooperating with the cutting channel formed in said holding plate.

7. A stitching mechanism as claimed in claim wherein said mechanism further comprises a removal means positioned below the workpiece support bed of the sewing machine for disposing of the loose piece of bobbin supplied material formed by the first and second cuts made thereon.

8. A stitching mechanism for a sewing machine having a workpiece support bed for controlling the formation of a terminal stitch in a terminating series and an initial stitch in a subsequent series, the terminal stitch and the initial stitch each having a restraining loop formed on the upper portion thereof, said mechanism comprising:

a stitch forming mechanism forming stitches in a workpiece, said stitch forming mechanism including a bobbin supplying a strand material for the stitch forming mechanism;

selectively actuatable positioning means coupled to said stitch forming mechanism for causing a first pause in the movement of the stitch forming mechanism prior to completion of the terminal stitch restraining loop and for causing a second pause prior to the completion of the initial stitch restraining loop;

holding means mounted between the workpiece support bed and the bobbin of the sewing machine, said holding means actuatable to deflect and hold the bobbin supplied material so that the initial stitch and the initial stitch restraining loop may be formed thereon after completion of the terminal stitch;

first cutter means movably mounted between the workpiece support bed and said holding means for severing the bobbin supplied material, said first cutter means operable during the first pause in the movement of the stitch forming mechanism to form a first free end on the terminal stitch, the first free end being moved adjacent to the workpiece by the stitch forming mechanism when it completes the terminal stitch restraining loop; and

second cutter means mounted below said holding means and operable during the second pause in the movement of the stitch forming mechanism for again severing the bobbin supplied material to form a second free end on the initial stitch, the second free end being moved adjacent to the workpiece by the stitch forming mechanism when it completes the initial stitch restraining loop.

9. A stitching mechanism for a sewing machine comprising:

a stitch forming mechanism forming stitches in a workpiece, said stitch forming mechanism including a bobbin supplying a strand material;

positioning means coupled to said stitch forming mechanism and selectively actuated to drive and stop said stitch forming mechanism in selected divisions of a stitch forming cycle; and

cutter means movably mounted adjacent the bobbin for severing the bobbin supplied material, said cutter means being actuated during a pause caused by said positioning means occurring prior to completion of a stitch to form a free end on the bobbin supplied material, said free end being adjacent to the workpiece by the completion of the stitch by the stitch forming mechanism.

l 10. A stitching mechanism for a sewing machine com a h t t tii fonning mechanism forming stitches in a workpiece;

first supply means for supplying an upper strand material for the upper portion of a stitch to said stitch forming mechanism;

second supply means for supplying a lower strand material for the lower portion of a stitch to said stitch forming mechanism;

positioning means connected to said stitch forming mechanism and selectively actuated to drive and stop said stitch forming mechanism in selected divisions of a stitch forming cycle; and

cutter means movably mounted for severing the lower strand material, said cutter means being actuated during a pause caused by said positioning means and occurring prior to completion of a stitch to form a free end on the lower strand material, said free end being moved adjacent to the workpiece by the upper strand material during the completion of the stitch by the stitch forming mechanism.

11. A stitching mechanism for a sewing machine comprising:

a stitch forming mechanism forming stitches in a workpiece;

first supply means for supplying an upper strand material for the upper portion of a stitch to said stitch forming mechanism;

second supply means for supplying a lower strand material for the lower portion of a stitch to said stitch forming mechanism;

positioning means connected to said stitch forming mechanism and selectively actuated to drive and stop said stitch forming mechanism in selected divisions of a stitch forming cycle;

first cutter means movably mounted for making a first cut in the lower strand material to form a first free end on the lower strand material of a terminal stitch in a series of stitches during a pause caused by said positioning means and occurring prior to completion of the terminal stitch, said first free end being moved adjacent to the workpiece by the upper strand material during completion of the terminal stitch by the stitch forming mechanism;

a gripper block;

a holding plate movably mounted below said first cutter means and in alignment with said gripper block, said holding plate and gripper block cooperating to deflect and hold the lower strand material for forming an initial stitch after completion of the terminal stitch; and

said holding plate having a cutting channel formed in the lower surface thereof into which the lower strand material moves during formation of the ini- 

1. A stitching mechanism for a sewing machine for severing of a bobbin supplied material of a stitch and for positioning a free end of the bobbin supplied material adjacent to a workpiece, said mechanism comprising: a stitch forming mechAnism forming stitches in a workpiece, said stitch forming mechanism including a bobbin supplying a strand material for the stitch forming mechanism; selectively actuatable positioning means coupled to said stitch forming mechanism for causing a pause in a movement of the stitch forming mechanism prior to completion of the stitch; and cutter means movably mounted for severing the bobbin supplied material during the pause prior to completion of the stitch caused by said positioning means to form a free end on the bobbin supplied material, the free end being moved adjacent to the workpiece by the stitch forming mechanism when it completes the stitch.
 2. A stitching mechanism as claimed in claim 1 wherein said positioning means comprises a pulse operated stepping motor.
 3. A stitching mechanism as claimed in claim 1 wherein said cutter means comprises: a lever movably mounted on the lower surface of the workpiece support bed and in contiguous engagement therewith; means coupled to one end of said lever for providing movement thereto; and a knife edge formed on the other end of said lever to cooperate with the workpiece support bed for severing the bobbin supplied material when said lever is moved relative to the bed.
 4. A stitching mechanism for a sewing machine for controlling the severing of a bobbin supplied material to form a first free end on a terminal stitch in a terminating series and to form a second free end on an initial stitch in a subsequent series and for positioning both the first and the second free ends adjacent to a workpiece, said mechanism comprising: a stitch forming mechanism forming stitches in a workpiece, said stitch forming mechanism including a bobbin supplying a strand material for the stitch forming mechanism; selectively actuatable positioning means coupled to said stitch forming mechanism for causing a pause in the movement of the stitch forming mechanism prior to completion of the terminal stitch and for causing another pause in the movement of the stitch forming mechanism prior to completion of the initial stitch; first cutter means mounted adjacent to the bobbin for severing the bobbin supplied material during the pause prior to completion of the terminal stitch to form the first free end thereon, the first free end being pulled adjacent to the workpiece by the stitch forming mechanism when it completes the terminal stitch; holding means mounted below said first cutter means for holding the severed bobbin supplied material, and for deflecting the bobbin supplied material into position for the formation of the initial stitch thereon; and second cutter means mounted below said holding means for severing the bobbin supplied material during the pause prior to completion of the initial stitch to form the second free end thereon, the second free end being pulled adjacent to the workpiece by the stitch forming mechanism when it completes the initial stitch.
 5. A stitching mechanism for a sewing machine for controlling the formation of a terminal stitch in a terminating series and an initial stitch in a subsequent series, said mechanism comprising: a stitch forming mechanism forming stitches in a workpiece, said stitch forming mechanism including a bobbin supplying a strand material for the stitch forming mechanism; selectively actuatable positioning means coupled to said stitch forming mechanism for causing a pause in the movement of the stitch forming mechanism prior to the completion of the terminal stitch and for causing another pause prior to completion of the initial stitch; first cutter means movably mounted below a workpiece support bed of the sewing machine for making a first cut in the bobbin supplied material to form a first free end on the terminal stitch during the pause prior to completion thereof, the first free end being moved adjacent to the workpiece by the stitch forming mechanism when it completes the terminal stitch; a gripper block fixedly mounted beLow the workpiece support bed of the sewing machine; a holding plate movably mounted below said first cutter means and in alignment with said gripper block for deflecting the bobbin supplied material into holding engagement with said gripper block so that the initial stitch may be formed on the bobbin supplied material after severing and completion of the terminal stitch, said holding plate having a cutting channel formed in the lower surface thereof into which the bobbin supplied material moves during formation of the initial stitch, said holding plate further having a slot formed in the lower surface thereof; and second cutter means movably mounted in the slot formed in said holding plate for cooperating with the cutting channel thereof to make a second cut in the bobbin supplied material during the pause prior to completion of the initial stitch to form a second free end thereon, the second free end being moved adjacent to the workpiece by the stitch forming mechanism when it completes the initial stitch.
 6. A stitching mechanism as claimed in claim 5 wherein said second cutter means comprises a plate having a cutter notch formed in one end thereof for cooperating with the cutting channel formed in said holding plate.
 7. A stitching mechanism as claimed in claim 5 wherein said mechanism further comprises a removal means positioned below the workpiece support bed of the sewing machine for disposing of the loose piece of bobbin supplied material formed by the first and second cuts made thereon.
 8. A stitching mechanism for a sewing machine having a workpiece support bed for controlling the formation of a terminal stitch in a terminating series and an initial stitch in a subsequent series, the terminal stitch and the initial stitch each having a restraining loop formed on the upper portion thereof, said mechanism comprising: a stitch forming mechanism forming stitches in a workpiece, said stitch forming mechanism including a bobbin supplying a strand material for the stitch forming mechanism; selectively actuatable positioning means coupled to said stitch forming mechanism for causing a first pause in the movement of the stitch forming mechanism prior to completion of the terminal stitch restraining loop and for causing a second pause prior to the completion of the initial stitch restraining loop; holding means mounted between the workpiece support bed and the bobbin of the sewing machine, said holding means actuatable to deflect and hold the bobbin supplied material so that the initial stitch and the initial stitch restraining loop may be formed thereon after completion of the terminal stitch; first cutter means movably mounted between the workpiece support bed and said holding means for severing the bobbin supplied material, said first cutter means operable during the first pause in the movement of the stitch forming mechanism to form a first free end on the terminal stitch, the first free end being moved adjacent to the workpiece by the stitch forming mechanism when it completes the terminal stitch restraining loop; and second cutter means mounted below said holding means and operable during the second pause in the movement of the stitch forming mechanism for again severing the bobbin supplied material to form a second free end on the initial stitch, the second free end being moved adjacent to the workpiece by the stitch forming mechanism when it completes the initial stitch restraining loop.
 9. A stitching mechanism for a sewing machine comprising: a stitch forming mechanism forming stitches in a workpiece, said stitch forming mechanism including a bobbin supplying a strand material; positioning means coupled to said stitch forming mechanism and selectively actuated to drive and stop said stitch forming mechanism in selected divisions of a stitch forming cycle; and cutter means movably mounted adjacent the bobbin for severing the bobbin supplied material, said cutter means being actuated during a pause caused By said positioning means occurring prior to completion of a stitch to form a free end on the bobbin supplied material, said free end being adjacent to the workpiece by the completion of the stitch by the stitch forming mechanism.
 10. A stitching mechanism for a sewing machine comprising: a stitch forming mechanism forming stitches in a workpiece; first supply means for supplying an upper strand material for the upper portion of a stitch to said stitch forming mechanism; second supply means for supplying a lower strand material for the lower portion of a stitch to said stitch forming mechanism; positioning means connected to said stitch forming mechanism and selectively actuated to drive and stop said stitch forming mechanism in selected divisions of a stitch forming cycle; and cutter means movably mounted for severing the lower strand material, said cutter means being actuated during a pause caused by said positioning means and occurring prior to completion of a stitch to form a free end on the lower strand material, said free end being moved adjacent to the workpiece by the upper strand material during the completion of the stitch by the stitch forming mechanism.
 11. A stitching mechanism for a sewing machine comprising: a stitch forming mechanism forming stitches in a workpiece; first supply means for supplying an upper strand material for the upper portion of a stitch to said stitch forming mechanism; second supply means for supplying a lower strand material for the lower portion of a stitch to said stitch forming mechanism; positioning means connected to said stitch forming mechanism and selectively actuated to drive and stop said stitch forming mechanism in selected divisions of a stitch forming cycle; first cutter means movably mounted for making a first cut in the lower strand material to form a first free end on the lower strand material of a terminal stitch in a series of stitches during a pause caused by said positioning means and occurring prior to completion of the terminal stitch, said first free end being moved adjacent to the workpiece by the upper strand material during completion of the terminal stitch by the stitch forming mechanism; a gripper block; a holding plate movably mounted below said first cutter means and in alignment with said gripper block, said holding plate and gripper block cooperating to deflect and hold the lower strand material for forming an initial stitch after completion of the terminal stitch; and said holding plate having a cutting channel formed in the lower surface thereof into which the lower strand material moves during formation of the initial stitch; and second cutter means movably mounted for forming a second free end by cutting the lower strand material held by said holding plate and gripper block during the pause prior to completion of the initial stitch, the second free end being moved adjacent to the workpiece by the stitch forming mechanism when it completes the initial stitch. 